Catalyst for preparation of ortho-alkylated phenols

ABSTRACT

The present invention provides an improved manganic oxide catalyst for the production of ortho-alkyl phenols by vapor phase reaction of a phenol having at least one ortho-hydrogen with an alcohol, the improvement comprises soaking manganic oxide in an aqueous solution of alkali metal salt, separating the soaked manganic oxide from the solution, drying and calcining the soaked manganic oxide at a temperature of 300°-600° C. for a period of 1-3 hours to form an alkali metal oxide thereon, wherein the weight ratio of the alkali metal oxide to the manganic oxide is 0.5-0.0001 wt %, preferably 0.1-0.0001 wt %.

This application is a continuation of application Ser. No. 07/410,833,filed Sept. 22, 1989, now abandoned.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a catalyst for preparation ofortho-alkylated phenols.

BACKGROUND OF THE INVENTION

Stephen B. Hamilton, Jr., in U.S. Pat. No. 3,446,856, first discloses amethod for methylating the ortho position of phenol by the vapor phasereaction of phenol with methanol in the presence of magnesium oxide as acatalyst at a temperature ranging from 475° to 600° C., in which theservice life of said catalyst at the typical reaction temperature ofabout 530° C. is about 90 to 100 hours, and the catalyst is puremagnesium oxide in powdered or sintered form which causes processingdifficulties due to its weak mechanical properties.

Van Sorge has developed several improved catalysts for the sameortho-alkylation process as disclosed by above mentioned U.S. patent,which comprises bonding magnesium oxide with suitable materials. In hisinventions of U.S. Pat. Nos. 3,843,606, 3,974,229, and 4,097,411, aninert organic polymer, manganese oxide, and silica are disclosed as abinder respectively. The bonded catalysts taught by Van Sorge, which maybe molded to any desired shape, generally have the followingimprovements such as excellent physical properties, a service life ofmany hundred hours, a catalyst bed temperature varying between 460° and500° C., and a higher degree of selectivity and yield.

Kong R. Chang and one of the inventors of present invention, Trong G.Lin in U.S. Pat. No. 4,546,093 disclosed a process for preparing3-component catalyst system consisting of manganic oxide, ferric oxideand zinc oxide, which is used for the catalytic synthesis of 2,6-xylenolfrom reacting phenol with methanol. This 3-component catalyst has animproved reaction activity and selectivity with comparison to themagnesium oxide catalyst taught by Van Sorge. However, the presentinvention further provides a process to promote this 3-componentcatalyst.

In co-pending application Ser. No. 07/206,834 filed in 1988, theinventors of present invention with co-inventors disclosed a catalystfor ortho-alkylation of phenols which is prepared by calcining aco-precipitate of magnesium salt and manganese salt. Furthermore, theytaught that an additional alkali metal oxide may be formed on thesurface of the alkylation catalyst to enhance its service life.

SUMMARY OF THE INVENTION

The present invention provides an improved manganic oxide catalyst forthe production of ortho-alkyl phenols by vapor phase reaction of aphenol having at least one ortho-hydrogen with an alcohol, theimprovement comprises soaking manganic oxide in an aqueous solution ofalkali metal salt, separating the soaked manganic oxide from thesolution and drying, and then calcining the soaked manganic oxide at atemperature of 300°-600° C. for a period of 1-3 hours to form an alkalimetal oxide thereon, wherein the weight ratio of the alkali metal oxideto the manganic oxide is 0.5-0.0001 wt %, preferably 0.1-0.0001 wt %.

Contemplated as the functional, or operative, equivalent of the manganicoxide for purpose of this invention is a mixture consisting of manganicoxide, ferric oxide and zinc oxide in which the atom ratio of Mn:Fe:Znis from 100:20:20 to 100:0.01:0.01.

Thus, the present invention relates to an improved catalyst for theproduction of ortho-alkyl phenols by vapor phase reaction of a phenolhaving at least one ortho-hydrogen with an alcohol comprising 100 partsby weight of manganic oxide, 0-20 parts by weight of ferric oxide, and0-20 parts by weight of zinc oxide, and said catalyst including analkali metal oxide, wherein the weight ratio of the alkali metal oxideto the catalyst is from 0.5-0.0001.

The improved manganic oxide catalyst provided by present invention willhave a significant longer service life, a higher reaction activity andselectivity with comparison to the prior art catalyst. Expecially, whenthe improved manganic oxide catalyst becomes deactivated over longperiods of operation, it can be repeatedly regenerated and still have acomparable reaction activity and service life.

DETAILED DESCRIPTION OF THE INVENTION

The improved manganic oxide catalyst of the present invention, activefor ortho-alkylation of phenols with an alcohol, is prepared by formingalkali metal oxide on the manganic oxide surface, in which the weightratio of alkali metal oxide to manganic oxide is 0.5-0.0001 wt %,preferably 0.1-0.0001 wt %. Normally, the alkali matal oxide isdeposited on the manganic oxide by impregnating the manganic oxide in anaqueous solution of alkali metal salt, separating the impregnatedmanganic oxide from the solution, and gradually drying the impregnatedmanganic oxide at an elevated temperature, and then calcining it at atemperature of 300°-600° C. for a period of 1-3 hours to form alkalimetal oxide on the manganic oxide.

The above mentioned aqueous solution of alkali metal salt is prepared bydissolving soluable alkali metal salt in water. Suitable alkali metalsalts are chlorides, nitrates, sulfates, acetates, oxalates and thelikes.

The manganic oxide used in present invention is preferably prepared bytreating an aqueous solution having solubilized manganic ions with analkali to form a precipitate of manganic salt; filtering the treatedsolution with water wash to a cake of the precipitate; drying said cakeand grinding into powders; molding said powders to a desired shape withan addition of water; and then calcining the molded articles at atemperature of 300°-600° C. for a period of about 1-3 hours. A surfacearea of at least 10 square meters per gram of manganic oxide isdesirable. The shape of the manganic oxide may be in the form ofRasching rings, cylinders, tablets or any other shape known to the art.

The aqueous solution having solubilized manganic ions is prepared bydissolving soluble manganic salt in water. Examples of suitable saltsare chlorides, nitrates, sulfates, acetates, oxalates and the likes.

The amount of the alkali used in the above mentioned preparation shouldbe such as to provide a complete precipitation of solubilized manganicions. Generally, the solubilized manganic ions will start precipitatingat a pH value of the solution of about 8.0, and it will reach a valueabout 9.3 or up at the end of said alkali treatment. Examples ofsuitable alkali are aqueous solution of ammonion hydroxide, potassiumhydroxide, sodium hydroxide, sodium carbonate, potassium carbonate,sodium hydrogen carbonate, potassium hydrogen carbonate and the likes.

A 3-component mixture of manganic oxide, ferric oxide and zinc oxidehaving an atomic ratio of Mn:Fe:Zn ranging from 100:20:20 to100:0.01:0.01 may be used in this invention instead of manganic oxide.The preparation of this 3-component mixture is disclosed in U.S. Pat,No. 4,546,093, details thereof are incorporated by reference.

The method for forming the ortho-alkylated phenols comprises avapor-phase reaction of an alkyl alcohol and a non-ortho-substitutedphenol in the presence of the catalyst of this invention at a catalystbed temperature of at least 300° C., and preferably at a temperature of380° to 500° C. In general, the process is similar to the processdisclosed in the above mentioned U.S. Pat. Nos. 3,446,856 and 3,974,229,the disclosure of which is incorporated herein as reference. However,the reaction temperature of the process is lower due to the higheractivity of the catalyst of this invention. The alkyl alcohol used inthe ortho-alkylation process is saturated alkyl alcohol, such asmethanol, ethanol, propanol, cylcohexanol, and saturated alkyl alcoholshaving carbon atoms less than 20, preferably less than 6, and mostpreferably methanol. The phenol used may be represented by the formula:##STR1## where each R is a monovalent substituent selected from thegroup consisting of hydrogen, alkyl, phenyl, and alkyl substitutedphenyl. Mainly, methanol, phenol or o-cresol are used in theortho-alkylation process to produce o-cresol or 2,6-dimethyl phenolproduct, especially 2,6-dimethyl phenol is most desired.

In order to obtain a higher yield of ortho-alkylated products, at least1 mole of an alkyl alcohol and preferably from 1 to 4 moles of thealcohol is used for each ortho position in the phenol to be alkylated.Also, if the feed contains less than about 20 wt % of water, thecatalyst will have a longer service life in the alkylation reaction.

The vapors issuing from the reactor are condensed and the products areseparated in conventional manner, such as by crystallization,distillation, etc. The reaction proceeds at atmospheric pressure, but itis obvious that pressures above or below atmospheric pressure may beused. Also, the reaction can proceed in any known type of reactors, suchas fixed bed reactor, fluidized bed reactor, isothermal reactor, etc.

When the catalyst becomes deactivated over long periods of operation, itcan be regenerated by oxidation of the carbon deposited thereon by meansof oxygen or air at flow rates such that the catalyst bed temperaturedoes not exceed the maximum of 600° C.

The examples presented below are presented only to illustrate theinvention and not meant to limit the scope of the invention. In all ofthe examples, precentages are by mole percents, unless otherwiseindicated.

CONTROL EXAMPLE 1 Preparation of the Catalyst: (Mn2O3)

1000 g of Mn(NO3)2.6H2O was added with stirring into 1200 ml deionizedwater. After the added salts dissolved completely, 28 wt % ammonia waterwas introduced slowly until the pH value of solution reached about9.0-9.2 to precipitate the solubilized metal ions and the mixture waskept stirring for another 0.5 hour. The mixture was filtered withdeionized water wash to yield a cake of precipitate. The cake was driedat a temperature of 120° C. for 3 hours or up, and grinded into powders.The powders were mixed with water and extruded into cylindrically shapedpellets having a diameter of 4 mm and a length of 4 mm. The pellets werecalcined at a temperature of 500° C. for 3 hours.

Preparation of 2,6-dimethyl phenol (2,6-DMP)

Phenol, methanol and water were mixed in a container equipped with ameasuring pump, wherein the mole ratio of phenol:methanol:water was1:6:1, and the mixture was charged into a fixed-bed isothermal reactorpreviously filled with 30 g catalyst made as aforementioned method at arate of 30 ml/hour. The effluent was condensed and collected in acondenser, and then analyzed by gas chromatography. The conditions andresults are summarized in run 1, Table 1.

EXAMPLE 1

The procedure of above control example 1 was repeated except that theMn2O3 catalyst was further promoted by K2O. 100 g Mn2O3 catalyst of thecontrol example 1 was impregnated in an aqueous solution containing0.0021 mg of KNO3 of 30 hours, the soaked catalyst was separated anddried gradually at a temperature of 110° C., and calcined at atemperature of 500° C. for 3 hours to form a K2O layer on the catalyst.The K2O content is 0.001 wt % based on the weight of Mn2O3 catalyst. Thereaction conditions and results of the ortho-alkylation process at thepresence of this promoted catalyst are listed in run 1a, Table 1.

CONTROL EXAMPLE 2 Preparation of the Catalyst: (Mn/Fe/Zn Oxides)

1000 g Mn(NO3)2.6H2O, 1.4 g Fe(NO3)3.9H2O, and 1.05 g Zn(NO3)2.4H2O wereadded with stirring into 1200 ml deionized water. After the added saltsdissolved completely, 28 wt % ammonia water was introduced slowly untilthe pH value of the solution reached about 9.0-9.2 to precipitate thesolubilized metal ions and the mixture was kept stirring for another 0.5hour. The mixture was filtered with deionized water wash to yield a cakeof precipitate. The cake was dried at a temperature of 120° C. for 3hours or up, and grinded into powders. The powders were mixed with waterand extruded into cylindrically shaped pellets having a diameter of 4 mmand a length of 4 mm. The pellets were calcined at a temperature of 500°C. for 3 hours. The mole ratio of Mn:Fe:Zn of the calcined catalyst inthis example is 100:0.1:0.1.

Preparation of 2,6-dimethyl phenol (2,6-DMP)

The procedure of preparation of 2,6-DMP in above control example 1 wasrepeated. The reaction conditions and results are listed in run 2, Table1.

EXAMPLE 2

The procedure of above control example 2 was repeated except that thecatalyst was further promoted by K2O. 100 g Mn/Fe/Zn oxides catalyst ofthe control example 2 was soaked in an aqueous solution containing0.0021 mg of KNO3 for 30 hours, the soaked catalyst was separated anddried gradually at a temperature of 110° C., and calcined at atemperature of 500° C. for 3 hours to form a K2O layer on the catalyst.The K2O content is 0.001 wt % based on the weight of Mn/Fe/Zn oxidescatalyst. The reaction conditions and results of the ortho-alkylationprocess at the presence of this promoted catalyst are listed in run 2a,Table 1.

EXAMPLE 3

The object of this example is to illustrate that the Mn2O3 catalysts canbe promoted by depositing different alkali metal oxides on theirsurface. The procedure of above example 1 was repeated with thesubstitution of different alkali metal salts. The conditions and resultsare listed in run 3 and 4 of Table 1, respectively.

                                      TABLE 1                                     __________________________________________________________________________    Reaction pressure 9 kg/cm2, WHSV.sup.(i) = 0.9 hr.sup.-1                                    Initial                                                                            Initial conversion.sup.(iii)                                                             Initial selectivity.sup.(iii)                                                            Service life.sup.(iv)                Run                                                                              Catalyst   temp. (°C.)                                                                  of phenol (%)                                                                           2,6-DMP                                                                            2,4,6-TMP                                                                           (hrs)                                __________________________________________________________________________    1  Mn2O3      420   99.74     85.99                                                                              4.36  697.5                                1a Mn2O3 +    440   100.0     92.68                                                                              5.05  914.0                                   0.001 wt % K2O                                                             2  Mn/Fe/Zn oxides                                                                          420   100.0     86.40                                                                              7.10  508.0                                2a Mn/Fe/Zn oxides +                                                                        420   99.76     89.36                                                                              7.68  724.0                                   0.001 wt % K2O                                                             3  Mn2O3 +    450   99.88     98.19                                                                              0.53  820.0                                   0.02 wt % Cs2O                                                             4  Mn2O3 +    460   100.0     93.12                                                                              4.75  --                                      0.05 wt % Li2O                                                             __________________________________________________________________________     .sup.(i) WHSV is the liquid hourly space velocity and defines the weight      of liquid per weight of catalyst per hour.                                    .sup.(ii) The conversion of phenol = [(moles of phenol reacted)/(moles of     phenol in the feed)] * 100%                                                   .sup.(iii) The selectivity is defined as the mole percents of 2,6dimethyl     phenol (2,6DMP) or 2,4,6trimethyl phenol (2,4,6TMP) based on the total        moles of alkylated phenols.                                                   .sup.(iv) The service life is defined as the time during which the            production rate of 2,6DMP is kept above 70% from the reaction start to a      reaction temperature of 480 C.                                           

As it is shown in Table 1 that the catalysts promoted forming a layer ofalkali metal oxides thereon have higher yield 2,6-DMP and prolongedservice life.

EXAMPLE 4

The object of this example is to demonstrate that when the improvedcatalyst of present invention becomes deactivated after long periodsoperation, the spent catalyst can be regenerated by introducing airthrough the catalyst bed and still have a comparable activity,selectivity, and service life.

The deactivated catalysts of above control example 1 and example 1 wereregenerated by introducing air through the catalyst bed with acontrolled temperature gradually arising from about 250° C. to 500° C.,respectively. The same regeneration procedure was repeated when thecatalysts had become deactivated after long periods operation in thepreparation of 2,6-DMP. The conditions and results are summarized in thefollowing Table 2.

                  TABLE 2                                                         ______________________________________                                        (reaction pressure 9.00 kg/cm.sup.2)                                                   No. of     Reaction   Service life                                                                          WHSV                                   Catalyst regeneration                                                                             Temp. (°C.)                                                                       (hrs)   (hr.sup.-1)                            ______________________________________                                        Mn2O3    0          420-480    191.0   2.40                                   Mn2O3    1          420-480    119.0   2.40                                   Mn2O3    2          430-480    119.0   2.40                                   Mn2O3    3          420-480    102.0   2.40                                   Mn2O3/K2O                                                                              0          440-480    913.0   0.90                                   Mn2O3/K2O                                                                              1          420-480    820.0   0.90                                   Mn2O3/K2O                                                                              2          430-460    860.0   0.90                                   Mn2O3/K2O                                                                              3          430-470    1200.0  0.90                                   Mn2O3/K2O                                                                              4          430-470    1320.0  0.90                                   ______________________________________                                    

What we claim is:
 1. An improved catalyst for the production of ortho-alkyl phenols by vapor phase reaction of a phenol having at least one ortho-hydrogen with an alcohol, wherein the improvement comprises a catalyst comprising a mixture of manganic oxide, ferric oxide and zinc oxide in which the atom ratio of Mn:Fe:Zn is from 100:20:20 to 100:0.01:0.01 and including an alkali metal oxide, wherein the weight ratio of the alkali oxide to the manganic oxide is from 0.5-0.0001.
 2. A catalyst as claimed in claim 1, wherein the weight ratio of the alkali metal oxide to the manganic oxide is 0.1-0.0001.
 3. A catalyst according to claim 2 wherein the alkali metal is potassium, cesium or lithium.
 4. A catalyst according to claim 3 wherein the alkali metal is potassium.
 5. A catalyst according to claim 1 which has a surface area of at least 10 m² /g of manganic oxide.
 6. An improved catalyst for the production of ortho-alkyl phenols by vapor phase reaction of a phenol having at least one ortho-hydrogen with an alcohol, wherein the improvement comprises a catalyst comprising a mixture of manganic oxide, ferric oxide and zinc oxide in which the atom ratio of Mn:Fe:Zn is from 100:20:20 to 100:0.01:0.01, wherein the catalyst is first impregnated in an aqueous solution of an alkali metal salt, separating the impregnated catalyst from the solution, drying the impregnated catalyst, and calcining the impregnated catalyst at a temperature of 300°-600° C. for a period of 1-3 hours to form an alkali metal oxide thereon, wherein the weight ratio of the alkali metal oxide to the manganic oxide is 0.1-0.0001. 